Appliance and process for introducing sealing compound into lug caps

ABSTRACT

Also disclosed is an appliance for introducing sealing compound into lug caps, the appliance containing a turntable for accommodating the cap, and an injection unit, the injection unit containing a nozzle block, which has annularly arranged injection nozzles, and a delivery device for the sealing compound, the turntable and the nozzle block being arranged so as to be centered and the nozzle block being rotatable in the same direction as the turntable. 
     The invention also relates to a process for introducing sealing compound into lug caps and to the use of the appliance for injecting sealing compound into lug caps.

FIELD OF THE INVENTION

The present invention relates to an appliance for introducing sealingcompound into lug caps. The invention further relates to a process forintroducing sealing compound into lug caps and to the use of theappliance for injecting sealing compound into lug caps.

BACKGROUND AND SUMMARY OF THE INVENTION

Lug caps are used to close packages such as jars and glass preserves.The purpose of the various packaging materials is hermetic sealing ofthe contents against the environmental effects, even under extremeconditions as exist, e.g., in the heat sterilization of foodstuffs. Inorder to ensure this insulation of the contents from the environment,lids and caps with which the package is closed have suitable sealingcompounds introduced thereinto. Commercially, i.e. economicallysatisfactory sealing compounds for closures must have a number ofcritical properties which make them into highly specialized materialsand compositions. Furthermore, the properties required of the sealingcompounds are also, inter alia, determined by the intended use of thepackagings.

In the case of packaging for foodstuffs, particular significanceattaches to the stability of the sealing compounds with respect to thecontents during sterilization or pasteurization, respectively, andduring the storage, often for years, of the packed foodstuffs. Normally,use is made, for caps and lids of packages made of metal, of sealingcompounds made of plasticizer-containing PVC plastisols as described, inthe case of caps for jars, for example in DE B-20 03 693. In addition tosaid PVC sealing compounds, sealing compounds based on polyurethane arealso known, however.

Sealing compounds can be applied in injection machines to the inside ofthe closures. In so doing, the problem arises on the production scalethat the introduction of the sealing compound can not always be carriedout in a defect-free manner, i.e. not always seamlessly. Also, highspinning speeds are often necessary on injection machines in order tocorrect any defects formed. The high spinning speeds are intended tosubsequently ensure a uniform distribution of the injected sealingcompound. Furthermore, complicated electronic control mechanisms arerequired for correcting the seams.

Moreover, it is difficult on the laboratory scale to manufacture, fortesting purposes, lug caps provided with sealing compounds. There is,however, the requirement of manufacturing, for testing purposes,internally coated lug caps provided with polymer compounds, in order totest the efficacy of newly developed sealing compounds and, inparticular, the efficacy of the sealing compounds on various innercoatings of the caps. Thus there is a need for a simple, cost-effectiveappliance for introducing sealing compounds to the previously coatedinside of lug caps or to coated circular blanks having asealing-compound sprue, which are inserted into neutral closures.

The object of the present invention therefore is to provide an appliancefor introducing sealing compounds into lug caps made of metal for testpurposes, i.e. at the laboratory scale. At the same time, the applianceshould be as cost-effective and practical as possible, function in asimple manner and insert the sealing ring with high accuracy. It shouldbe possible, by providing said appliance, to dispense with the otherwiserequired occupation of production lines. By means of the appliance to benewly developed, it should be possible to carry out in a rapid andsimple manner sterilization tests or the testing of the caps on thepreserve jars, using a very wide variety of sealing compounds and a verywide variety of coating systems for the inner coating of the caps.Introduction of the sealing compound is to take place uniformly withaccurate compound coverage and without discernable seams. The appliance,to be operated on a laboratory scale, should be able to dispense withhigh spinning speeds which have hitherto been in general usage ininjection machines for sealing compounds in order to correct defects.Moreover, no complicated electronic control mechanisms for correctingthe seams should be required.

The object of the present invention is achieved, surprisingly, by anappliance for introducing sealing compound into lug caps, which ischaracterized in that the appliance contains a turntable foraccommodating the cap, and an injection unit, the injection unitcontaining a nozzle block, which has annularly arranged injectionnozzles, and a delivery device for the sealing compound, the turntableand the nozzle block being arranged so as to be centered and the nozzleblock being rotatable in the same direction as the turntable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic perspective view of an apparatus forintroducing sealing compound into lug caps according to the invention.

FIG. 2 is a view taken along section line 2--2 of FIG. 1.

DETAILED DESCRIPTION

Referring now to the figures in the 10 turntable of the applianceaccording to the invention, precoated lug caps 12 or neutral closureswith a precoated stamped-out circular blank made of tin plate oraluminum are inserted and secured. In order to produce the circularblanks, plate body blanks, e.g. in DIN A 4 Format, are provided, on alaboratory scale, on a laboratory coating machine or with the aid of adoctor rod, with an inner coating which usually consists of a primer andan adhesive coating. Suitable materials for the inner coating of the lugcaps are coatings conventionally used in the packaging industry, basedon epoxy-phenol resin, acrylate resin, polyester or organosols. Thesecoatings are known (cf. e.g. H. Kittel, Lehrbuch der Lacke undBeschichtungen Textbook of Paint and Coatings!, Volume IV, Lack- andBeschichtungssysteme, Formulierung, Paint and coating systems,formulation!, Pub. W. A. Colomb. within H. Heenemann GmbH,Berlin-Oberschwandorf 1976) and therefore need not be described indetail.

Then circular blanks are stamped out, for example on an Erichsenblanking machine or in a cutting die in a toggle press, which blanksmay, e.g., have a diameter of 64 mm for Standard 63 lug caps. Within thestamped-out circular blanks, a sealing-compound sprue is accuratelyformed separately in the embossing die, for example by means of springcushion and clamping ring. This can likewise be done in a toggle press.In the case of the appliance according to the invention, the stamped-outcircular blanks provided with the inner coating are inserted and securedin the lid and are inserted into the turntable.

Alternatively it is of course possible to insert finished lug capsprovided with an inner coating into the turntable of the applianceaccording to the invention.

The turntable and the nozzle block may be driven in any way required.Preferably, they are driven by separate, continuously controllableelectric motors.

The injection unit 14 of the appliance according to the inventioncontains a nozzle block 16 with annularly arranged injection nozzles 17.Preferably, the application appliance contains from 14 to 22 annularlyarranged injection nozzles, for a mean cap diameter of from 53 to 77 mm.Preferably, the spacing between the annularly arranged injection nozzlesis from 8 to 14 mm. Of course, larger or smaller spacings are alsopossible. If the spacings are larger, the nozzle block should be rotatedin the same direction, so as to lead or follow the turntable, whereas inthe case of smaller spacings between the injection nozzles, the nozzleblock should be rotated in the same direction and synchronously with theturntable. The radius of the circle formed by the injection nozzles mustof course match the lid size. The size of the circle formed by theinjection nozzles must be designed in such a way that the sealingcompound, during injection, reaches the shaped sealing-compound sprue.Preferably, the sealing compound, during injection, reaches the centerof the sealing-compound sprue. It is therefore preferable for theinjection nozzle arrangement to be replaceable and thus to be adjustableto the lid size in each particular case.

Preferably, the injection nozzles are arranged in such a way that thesealing compound arrives vertically downwards on the inside of the lid.Of course, alternatively the injection nozzles can be arranged in such away that the angle between the lid plane and the injected compoundextrudate is not 90° C. The angle can be chosen variably, in order toensure that different lid sizes are matched.

Of course, the injection unit can be equipped with a controllableheating system in order to be able to bring the sealing compound and theinjection head to a suitable temperature.

By means of a different rotational-speed setting at the nozzle block andat the turntable, the injection angle of the sealing-compound extrudatewith respect to the lid plane is varied. The optimum injection angleresults from the flow behavior of the sealing compound.

The injection unit of the appliance according to the invention maycontain any delivery devices 18 desired for conveying the sealingcompound to the injection nozzles. Thus, conveying the sealing compoundmay, for example, be effected under computer control. Preferably, theinjection unit contains a cylinder for holding the sealing compound, anda piston which forces the sealing compound from the cylinder into thenozzle block and into the injection nozzles arranged thereon,respectively.

Opening and closing the injection nozzles can be effected in any waydesired, e.g. by computer-controlled injector needles or via a closurering which is situated on the nozzle block. When low-viscosity sealingcompounds are processed it is possible, in addition, to employ a set ofinjector needles for closing the injection nozzles automatically.

The nozzle block is driven in the same direction as the turntable, withthe option of adjusting the speed with respect to the turntable so as tolead or follow or run synchronously. In this context it is particularlypreferable for the turntable and the nozzle block to be able to bedriven at a variable rotational speed.

The co-rotation of the lid in the turntable and the injection nozzles inthe nozzle block ensures uniform injection of the sealing compound. Inthis arrangement, the appliance according to the invention has theadvantage that high spinning speeds can be dispensed with. Because thereis no transition at the seams, the accumulation and deficiency ofsealing compound at the critical points are prevented.

The present invention further relates to a process for introducingsealing compound into lug caps, which is characterized in thatstamped-out circular blanks provided with an inner coating are shaped,for the sealing compound application, and inserted into neutral caps andthese are inserted into a turntable, or lug caps provided with an innercoating are inserted in a turntable, by means of a delivery device thesealing compound arrives in a nozzle block having annularly arrangedinjection nozzles, and the sealing compound, with the turntable and thenozzle block rotating in the same direction, is applied to thestamped-out circular blanks or into the lug caps, respectively.

Preference is given to a process according to the invention, in whichthe sealing compound is applied to the circular blanks or to the lugcaps, respectively, by means of from 14 to 22 annularly arrangedinjection nozzles for a mean cap diameter of from 53 to 77 mm.Preferably, the spacing between the annularly arranged injection nozzlesis from 8 to 14 mm. Preferably, the application of the sealing compoundtakes place at a rotational speed of turntable and nozzle block between20 and 50 rpm. The co-rotation of the lid in the turntable and theinjection nozzles in the nozzle head ensures extraordinarily uniforminjection of the sealing compound.

According to the process of the invention, the turntable and the nozzleblock can be driven in any way desired. Preferably, they are driven byseparate, continuously controllable electric motors.

The delivery device for the sealing compound can be chosen at will.Thus, conveying the sealing compound may, for example, be effected undercomputer control. A process is preferred in which a piston forces thesealing compound contained in a cylinder into the nozzle block havingthe annularly arranged injection nozzles.

According to the process of the invention, the operation of opening andclosing the injection nozzles can be effected in any way desired.Preferably, a closure ring at the nozzle block is opened and, toterminate the sealing compound application, is closed again. Whenlow-viscosity sealing compounds are processed it is possible to employ,in addition, a set of injector needles for automatic closure of theinjection nozzles.

Preferably, the turntable and the nozzle block can be driven at avariable rotational speed. By means of a different rotational-speedsetting at the nozzle block and at the turntable, the injection angle ofthe compound extrudate with respect to the lid plane is varied. Theoptimum injection angle in the process according to the inventiondepends on the flow behavior of the sealing compound.

The sealing compounds applied according to the process according to theinvention are as a rule fused at approximately 220° C. and approximately60 sec.

The invention likewise relates to the use of the above-describedappliance for injecting sealing compound into lug caps or intostamped-out circular blanks for neutral caps. In this context, the lugcaps can be internally coated with a wide variety of coatings.

WORKING EXAMPLE:

A lug cap (φ 63 mm), internally coated with an epoxyphenol resin-basedprimer and with an organosol-based adhesive coating is inserted into theturntable. The number of the annularly arranged injection nozzles in theinjection unit is 18. The injection unit contains a cylinder, providedfor holding the sealing compound, and a piston as a delivery device forthe sealing compound. The compound composition introduced into thecylinder is a PVC-based sealing compound. The sealing compound ispreheated to 38° C. by means of a heating device. The nozzle block andthe turntable are driven in the same direction, at a rotational speed of20 rpm by means of separate, continuously controllable electric motors.The closure ring at the nozzle block is opened, and the piston pressureon the compound composition is set to 0.5 bar. After 1 sec. the closurering is closed again. The applied sealing compound is then dried for 60sec at 220° C. The layer thickness of the compound composition is 1 mm.After 24 h, a sterilization test is carried out.

To this end, a test solution (conc. acetic acid and edible oil 1:1) areintroduced into a container sealed by the lug cap, and the sterilizationtest is carried out under the conditions 121° C./1 h. The back pressureon the cap is 2 bar.

Result: the vacuum has been maintained. The adhesion of the sealingcompound to the adhesive coating is adjudged to be very good. Thesealing compound has not been cut.

What is claimed is:
 1. An apparatus for introducing sealing compoundinto lug caps comprising a turntable for accommodating a lug cap and aninjection unit, the injection unit containing a nozzle block havingannularly arranged injection nozzles extending in the direction of theturntable for delivering sealing compound into the lug cap and adelivery device for delivering the sealing compound to the nozzle block,the turntable and the nozzle block being arranged so as to be centeredwith respect to each other and the nozzle block being rotatable in thesame direction as the turntable; wherein the turntable and the nozzleblock are driven by separate, continuously controllable electric motors.2. An apparatus according to claim 1, wherein the nozzle block containsfrom 14 to 22 annularly arranged injection nozzles, for a mean capdiameter of from 53 to 77 mm.
 3. An apparatus according to claim 1wherein the spacing between the annularly arranged injection nozzles isfrom 8 to 14 mm.
 4. An apparatus according to claim 1 wherein theturntable and the nozzle block can be driven at a variable rotationalspeed.
 5. An apparatus according to claim 1 wherein the injection unitcomprises a cylinder for holding a sealing compound, and a piston as adelivery device for the sealing compound.
 6. An apparatus according toclaim 1 wherein there is situated, at the nozzle block, a closure ringfor opening and closing the injection nozzles.
 7. Process forintroducing sealing compound into lug caps, comprising(i) inserting intoa turntable a lug cap provided with an inner coating or circular blankshaving an inner coating and inserted into a neutral cap, (ii) deliveringthe sealing compound by means of a delivery device, to a nozzle blackhaving annularly arranged injection nozzles, the turntable and thenozzle block rotating in the same direction, and (iii) applying thesealing compound to the circular blank or into the lug cap, wherein theturntable and the nozzle block are driven by separate, continuouslycontrollable electric motors.
 8. Process according to claim 7, whereinthe sealing compound is applied to the circular blank or to the lug cap,by means of from 14 to 22 annularly arranged injection nozzles for amean cap diameter of from 53 to 77 mm.
 9. Process according to claim 7wherein the spacing between the annularly arranged injection nozzles isfrom 8 to 14 mm.
 10. Process according to claim 7 wherein theapplication of the sealing compound takes place at a rotational speed ofturntable and nozzle block between 20 and 50 rpm.
 11. Process accordingto claim 7 wherein the turntable and the nozzle block are driven at avariable rotational speed.
 12. Process according to claim 7 wherein apiston forces the sealing compound contained in a cylinder into thenozzle block having the annularly arranged injection nozzles. 13.Process according to claim 7 wherein a closure ring situated at theinjection unit is opened to allow application of the sealing compoundand, is closed to terminate the sealing compound application.